I admit to feeling quite smug. I had 110,000 nearly flawless miles on my LR4, until last year. I was so happy that all the problems everyone was having seemed to be avoiding me. I had almost no problems, did the crossovers, LCAs, an alternator, that was about it for 10 years.
Since December 2024 I’ve been stranded 3 times.
I’ve Replaced:

Front diff, front driveshaft, rear diff, rear driveshaft, skid plate, air compressor, other work on air suspension, and just a few days ago upper and lower control arms. Exactly one day after the control arms, I’m on bump stops. Again. Aggghh
So the question, where should I start on my diagnosis? Is there a way to get it pumped back up with the GAP tool? As far as I know, I can’t clear red faults.

I’m wondering if the mechanics knocked or pinched something when putting on the control arms? I only drove 30 miles or so with new arms until the red fault. Honestly, I’m thinking coil spring conversion. I’d really like to drive more than a few miles from my house with some assurance of getting back.
I LOVE this truck, I think more so than my Defender 130. I have to decide when enough is enough.

 

If you have a GAP tool, why not post the codes? There can be numerous reasons you are on the bumps and there are even causes that may not be air ride related but a fault some other place. You also do not mention any mods so I assume none, but if you have those silly sensors height rods they can cause issues for sure too. And I am a bit shocked by all that has been replaced too. My 06 D3 still has the original diff and front shaft, replaced the rear only because the center support was shot and I suspected the joints would be worn too at that point.

 

I think we might need some of the back story on all of this, as you've replaced a whole bunch of parts and assemblies that we don't hear of very often. Both differentials, both driveshafts are not something you often hear of being replaced.Let us know what was going on to get you to this point , Gap codes if you have them .

In your case the first item I would check might be the ABS sensor wires. We had the right front wire rubbed through by a sloppy Walmart tire installer and it dropped us on the stops while we were on the freeway with no warning at all. I spliced it back together in the Autozone parking lot and like a lot of other temporary fixes it's still on that Rover. As DT mentioned, it's not a suspension related fault but drops you immediately.

 

I just parked it on the stops last night. I really didn't expect to be able to do anything to get it up since I couldn't a year ago. But I went out this morning and cleared a code (didn't write it down, it was something about right front sensor). Lo and behold, it lifted back up. Reflecting on it, I'm almost certain my mechanic inadvertently screwed it up. They were having a lot of trouble with the Lucky8 upper control arm on that side, another story and pretty unhappy with them atm. I'm going to check the wires for corrosion and see what else I can see but it's holding air right now. I hope I see something obvious so I can have at least a little faith in it.

As for the rest of the problems, just a run of bad luck I guess? I don't know the nomenclature, but the gear or whatever between the front drive shaft and the front differential wore out and just spun. So those got replaced. Incidentally, found out that if the front axle isn't turning, the back axle won't either. So I was completely stranded with that one.
Last summer I went on vacation and the back wdiff as making a grinding noise. Made it home 200 miles but it was full of shavings and got replaced. And honestly I don't remember but there was 'something' that wore out between the transfer case and the rear axle and for whatever reason had to replace the whole axle to get that new part.
The gas tank skid plate was just rusted out, no big deal. The compressor was found to be weak (supposedly) when they were fixing the air system the first go around. I'm actually not sure what they did to fix it at the time, but it wasn't too expensive.

 

I did have to replace a rear diff, and replaced way too much before replacing the rear diff because I really did not want to tackle that job before doing everything else. It was making noise, but at least it seemed like it wasn't going to leave us stranded. Sounds like you have had a run of bad luck.

 

@roverrex Diffs are usually, not always lack of maintance - the oil level needs to be checked regularly, as in at least once a year. I do mine every 6 months